Improvement of Intake Restrictor Performance for a Formula SAE Race Car through 1D & Coupled

1D/3D Analysis Methods

Mark Claywell & Donald Horkheimer University of Minnesota

2006-01-36542

Agenda• Background• 1D Simulation Setup & Results• Coupled 1D/3D Simulation Setup & Results

• Volumetric Efficiency • Flow measurements- Mach Number, Turbulent

Kinetic Energy, & Total Pressure

• Acoustic Filtering for Volumetric Efficiency• Flow Control• Conclusions

2006-01-36543

Background• Overall Goal: Reduce the impact of the restrictor on

VE• Achieve a better understanding of flow in different restrictors• Look for areas to reduce flow losses

• Ricardo WAVE 1D model used with acoustic quality mesh in intake manifold• Multiple iterations quickly solved• Poor modeling of flow losses in diffuser section• Tuning impact of restrictor

• Ricardo WAVE coupled with Ricardo VECTIS (CFD) to model full intake• More accurate losses in diffuser• No need for end corrections at runner to plenum junctions• Very long run times = fewer design iterations

2006-01-36544

Description of Intake Manifold Geometry

DiffuserHalf-Angle

TotalHeight

Plenum Height

Diffuser Height

DiffuserVolume

PlenumVolume

Total Volume = Plenum + Diffuser Volume

Diffuser Exit Diameter

2006-01-36545

Case 1: Same Plenum Used

Difficult to get a clear trend of how diffuser angle affects tuning

■ Large changes in tuning across the rev range■ Both total length and total volume are changing

Diffuser Half-Angle 3° 4° 5.5° 7°

Diffuser Exit Diameter (mm) 72.90 72.90 72.90 72.90

Diffuser Length (mm) 504.7 378.2 274.7 215.4

Diffuser Volume (liters) 0.95 0.71 0.52 0.40

Plenum Volume (liters) 2.26 2.26 2.26 2.26

Plenum Length (mm) 160.5 160.5 160.5 160.5

Total Length from Throat to Plenum Bottom (mm)

665.2 538.7 435.2 375.9

Total Volume After Throat (liters)

3.21 2.97 2.78 2.66

2006-01-36546

Standing Waves - Case 1

2nd Order 4th Order 6th Order

4°

7°

11,000 RPM

14,000 RPM

2006-01-36547

Case 2: Equal DiffuserLengths

Diffuser length had large impact on tuningTotal volume had little impact on tuning

■ VE did not increase with increasing total volume

Diffuser Half-Angle 3° 4° 5.5° 7°

Diffuser Exit Diameter (mm) 42.578 50.126 61.485 72.898

Diffuser Length (mm) 215.4 215.4 215.4 215.4

Diffuser Volume (liters) 0.17 0.22 0.31 0.40

Plenum Volume (liters) 2.25 2.25 2.26 2.26

Plenum Length (mm) 160.5 160.5 160.5 160.5

Total Length from Throat to Plenum Bottom (mm)

375.9 375.9 375.9 375.9

Total Volume After Throat (liters)

2.423 2.474 2.564 2.663

2006-01-36548

WAVE-VECTIS Setup

Assumptions•WAVE-VECTIS junctions placed near 1D flow areas•No throttle body•No fuel spray particles in CFD domain•k-ε turbulence model•Full intake modeled for each diffuser change•Iterations in WAVE-VECTIS same as Case1 – Same Plenum Used

Inlet Box

2006-01-36549

VECTIS – Mesh Details

3.5mm1.75mm

~ 600,000+ cells

2006-01-365410

Theoretical Maximum Volumetric Efficiency Through a Restrictor Orifice

Engine Air Flow Demand SecondPerCyclesntDisplacemeQnom **21

.

0

00

11

*

1

2

pA

Qthroat

choked

Maximum Isentropic Flow Through an Orifice Area

.

max..nom

choked

Q

QEV

Maximum Theoretical Volumetric Efficiency(Limited by Restrictor)

Implicit Assumptions:

•Steady state flow

•Restrictor throat is choked 100% of the cycle

•Flow through restrictor equals flow through the intake valves.

•No pulse tuning effects

2006-01-365411

Volumetric Efficiency Predictions (CASE 1)

0.85

0.90

0.95

1.00

1.05

1.10

1.15

1.20

1.25

9000 10000 11000 12000 13000 14000 15000RPM

VO

LU

ME

TR

IC E

FF

ICIE

NC

Y

Theoretical Maximum

7 Degree - WAVE

5.5 Degree - WAVE

4 Degree - WAVE

3 Degree - WAVE

0.85

0.90

0.95

1.00

1.05

1.10

1.15

1.20

1.25

9000 10000 11000 12000 13000 14000 15000RPM

VO

LU

ME

TR

IC E

FF

ICIE

NC

Y

Theoretical Maximum7 Degree - WAVE 7 Degree - WAVE-VECTIS 5.5 Degree - WAVE 5.5 Degree - WAVE-VECTIS 4 Degree - WAVE 4 Degree - WAVE-VECTIS 3 Degree - WAVE 3 Degree - WAVE-VECTIS

0.85

0.90

0.95

1.00

1.05

1.10

1.15

1.20

1.25

9000 10000 11000 12000 13000 14000 15000RPM

VO

LU

ME

TR

IC E

FF

ICIE

NC

Y

Theoretical Maximum

Typically defined as the “choke point” of the restrictor

2006-01-365412

Volumetric Efficiency Comparison – 1D vs. 1D/3D vs. Theoretical Maximum

Theoretical Maximum

Wave-Vectis

WaveDifference

(Wave - W-V)

Difference (Wave-Vectis -

Theoretical Max.)

7° 10 126.5% 97.2% 103.7% 6.5% -29.3%

4° 10 126.5% 101.3% 105.3% 4.0% -25.2%

7° 11.5 110.0% 100.5% 107.9% 7.4% -9.5%

7° 14 90.4% 87.8% 93.7% 5.9% -2.6%

5.5° 14 90.4% 90.3% 93.2% 2.9% -0.1%

4° 14 90.4% 91.3% 92.9% 1.6% 0.9%

3° 14 90.4% 91.7% 94.3% 2.6% 1.3%

Half Angle

RPM x1000

VOLUMETRIC EFFICIENCY

2006-01-365413

CFD Results - Mach Number, Time AveragedPlanar Mean Mach Number at 14,000 RPM

(Time Averaged)

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0

Normalized Area

Mac

h [#

]

7° 5.5° 4° 3°

2006-01-365414

CFD Results – Mach, Time Avg.- 14,000 RPM

3°

4°

5.5°

7°

2006-01-365415

Velocity over one cycle – 14,000 RPM

•Movies frames are at 5° CAD resolution•Scale peak at 347m/s

7° 4°

2006-01-365416

Mach Number – Over One Cycle (1D/3D), 14,000 RPM

Restrictor Half Angle

RPM% of Cycle

Choked7° 10,000 0%4° 10,000 15.3%7° 11,500 0%7° 14,000 47.9%

5.5° 14,000 68.0%4° 14,000 80.0%3° 14,000 83.3%

7° 4°

2006-01-365417

Mach Number – Over One Cycle (1D/3D),10,000 RPM

• 4° achieves supersonic velocities yet outperforms 7°

7° 4°

2006-01-365418

Flow Uniformity of Mach NumberFlow Uniformity of Mach Number at 14,000 RPM

(Time Averaged)

0.60

0.65

0.70

0.75

0.80

0.85

0.90

0.95

1.00

1 2 3 4 5 6 7 8 9 10 11 12 13

Normalized Area

Flo

w U

nifo

rmity

Ind

ex_

7° 5.5° 4° 3°

Flow Uniformity of Mach Number at 10,000 RPM(Time Averaged)

0.60

0.65

0.70

0.75

0.80

0.85

0.90

0.95

1.00

1 2 3 4 5 6 7 8 9 10 11 12 13

Normalized Area

Flo

w U

nifo

rmity

Ind

ex_

7° 4°

2006-01-365419

Turbulent Kinetic Energy (TKE) – Time Averaged

Planar Mean Turbulent Kinetic Energy at 14,000 RPM(Time Averaged)

0

200

400

600

800

1000

1 2 3 4 5 6 7 8 9 10 11 12 13

Normalized Area

Tur

bul

ent

Kin

etic

Ene

rgy

[m2 /s

2 ] 7° 5.5° 4° 3°

Planar Mean Turbulent Kinetic Energy at 10,000 RPM(Time Averaged)

20

40

60

80

100

120

140

1 2 3 4 5 6 7 8 9 10 11 12 13

Normalized Area

Tur

bule

nt K

inet

ic E

nerg

y [m

2 /s2 ]

7° 4°

2006-01-365420

T.K.E. – One Cycle at 14,000 RPM

4°

5.5°

7°

3°

2006-01-365421

TKE vs. Mach4° at 14,000 RPM

Rising Mach #

Minimum TKEPeak TKE

Falling Mach #

2006-01-365422

Turbulent Kinetic Energy Over One Cycle

7° 4°

2006-01-365423

Total Pressure – Time AveragedPlanar Mean Total Pressure at 14,000 RPM

(Time Averaged)

78

79

80

81

82

83

84

85

86

87

88

89

90

1 2 3 4 5 6 7 8 9 10 11 12 13 14Normalized Area

Tot

al P

ress

ure

[kP

a]

7° 5.5° 4° 3°

• Total Pressure at diffuser did not agree well with VE• Total Pressure loss vs. TKE shows good agreement

Planar Mean Total Pressure at 10,000 RPM(Time Averaged)

95.4

95.8

96.2

96.6

97.0

97.4

97.8

98.2

98.6

99.0

1 1.25 1.5 1.75 2 2.25 2.5 2.75 3Normalized Area

Tot

al P

ress

ure

[kP

a]

7° 4°

2006-01-365424

Total Pressure – Time Averaged

7°

5.5°

4°

3°

2006-01-365425

Total Pressure Over One Cycle, 4° at 14,000 RPM

2006-01-365426

Total Pressure Over One Cycle 4° at 14,000 RPM

2006-01-365427

Acoustic Filtering (WAVE Only)• Reduce unsteady flow

through use of acoustic filtering

• Pressure pulse frequency given by:

• Helmholtz resonator used to attenuate desired frequency

• Plenum volume used mesh with 15mm cell size

30

*#

K

CylindersofOrderEngineRPMf

2006-01-365428

Acoustic Filtering

• Helmholtz Resonator A tuned for 442 Hz or 13,260 RPM (1st E.O.)

• Vol. = 0.761 liters• Helmholtz Resonator B tuned for 416 Hz or 12,480 RPM (1st E.O.)

• Vol. = 0.856 liters• Mesh held constant between different cases

2006-01-365429

Flow Effects of Adding Helmholtz Resonator A at 13,750 RPM

• Pressure & Velocity variation decreased• % cycle choked increased• Can not ascertain possible influence on separation with WAVE

2006-01-365430

Flow Control – Swirl Vanes• Reduce onset of separation after throat by increasing dynamic radial pressure component

• Flow separation reduction found in SAE 2003-01-0840

• Impart radial momentum through use of swirl vanes.

• Used with 7 Degree Restrictor•Run at 14,000 RPM•VE within 0.1%

2006-01-365431

Swirl Vanes vs. No Swirl Vanes – 14,000 RPM

With Swirl Vanes No Swirl Vanes

2006-01-365432

Conclusions Length of the intake plays an important role in VE curve; not just

volume Lower diffuser angles provided:

■ Lower TKE values■ Higher percentage of cycle achieving choked flow through the throat■ Better flow uniformity at 10,000 & 14,000 RPM■ Volumetric Efficiency closer to that predicted by WAVE■ Increased time averaged total pressure at the diffuser exit

3° & 4° restrictors achieved VE numbers greater than steady state based Theoretical Maximum VE

Peak TKE values occurred during falling Mach numbers, due to adverse pressure gradient.

Flow separation occurred for all diffuser angles and occurred at approximately the same area ratio

Acoustic filtering provided encouraging results in increasing VE, albeit in a narrow rpm range

Swirl vane flow control devices■ Intangible benefit to Volumetric Efficiency■ Reduced TKE values, but also Total Pressure■ Possible Benefits at lower RPM or with more fine tuning?

2006-01-365433

ACKNOWLEDGEMENTS• Minnesota Supercomputer Institute• Ricardo – Patrick Niven & Karl John• Univ. of Minnesota – Mechanical

Engineering• Dr. Patrick Starr• Dr. David Kittleson• Dr. William Durfee

• Kim Lyons – Daimler-Chrysler• Minnesota State University Mankato – Dr. Bruce Jones

QUESTIONS ?

2006-01-365435

Static Pressure – Time AveragedPlanar Mean Static Pressure at 14,000 RPM

(Time Averaged)

40

45

50

55

60

65

70

75

80

85

1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0

Normalized Area

Sta

tic P

ress

ure

[kP

a]

7° 5.5° 4° 3°